Just one? For two players: Scrabble or Carcassonne. For three or four players: Settlers of Catan, Puerto Rico If you can find them: Titan Talisman 2nd Edition

Just one? For two players: Scrabble or Carcassonne. For three or four players: Settlers of Catan, Puerto Rico If you can find them: Titan Talisman 2nd Edition and Illuminati are also totally awesome.